The present invention relates to groundwater sampling systems, and more particularly, to a vacuum driven ground water sampling system for collecting groundwater samples from shallow wells.
Submersible pumps have been used where the depth to the water is more than 25 feet below ground surface (ft bgs). Most environmental monitoring wells are completed in the uppermost water hearing formation. In most of the United States the depth to water is less than 25 ft bgs. There are several problems with using existing submersible pumps.
When using a submersible pump, the pump, electrical line, and tubing must be decontaminated prior to sampling each well. Decontamination prevents cross-contamination between wells, assuring quality control of the sampling activities. Proper decontamination is a time consuming process. In addition, in anomalous sample results are obtained, additional time and expense are required to address the anomalous results in a sampling report and the possible incurring of the expense of resampling.
When using a submersible pump, it is difficult for one person to handle the pump, electric line and tubing keeping all components off of the ground as required by standard sampling protocol to prevent possible cross-contamination. Sampling is much easier for two people, however, labor is a significant portion of the expense of groundwater sampling and while the second person makes sampling easier, they have little effect on sampling times.
In many cases, the groundwater removed from monitoring wells contains significant concentrations of compounds that are considered by the United States Environmental Protection Agency to be hazardous to human health. A health and safety plan is required to be prepared for all sites so that exposure of sampling personnel to these compounds is identified and minimized. When using submersible pumps, the water in the discharge lines should not be allowed to drain back into the well, to prevent cross-contamination and to minimize the effect the pumping has on water chemistry. Often, the water in the discharge lines ends up being drained on the ground and presents an exposure to sampling personnel.
Small submersible pumps designed to work in 2-inch diameter wells are sensitive to handling any abrasive material which is a frequent occurrence in groundwater sampling. In addition to damage to the impeller of any centrifugal type pump, the small submersibles have Teflon wear surfaces rather than bearings. These wear surfaces are very sensitive to abrasion and frequent maintenance is required.